In the treatment of storm water, it is necessary to remove various undesirable elements and components, such as bacteria, oil, metals, nutrients, trash and a number of other solids. Many of the pollutants bond to the finer sediment and which is the reason many regulatory agencies now focus on total suspended solids (TSS) as a criteria for design/approval of stormwater quality measures.
To that end, the Clean Water Act requires some stormwater quality treatment for all new developments over 0.5 acres in size. Many types of equipment and processes have been suggested for dealing with this problem.
One of the difficulties in the removal of such materials from stormwater is the need to take into account different flows of that water. For example, under normal conditions, there may be a steady, relatively low flow of water that passes through the treatment facility, while at other times, there is a heavy storm and the flow rapidly turns into a high flow and, therefore, the stormwater treatment facility needs to also be able to handle that high flow of water to be treated.
The devices need to be capable of trapping both floating and non-floating debris under both flow conditions efficiently and at a low cost of the equipment.
One of the problems in dealing with both high and low flows is that the debris and other material may be effectively removed and settled in the particular stormwater equipment at the low flow conditions, however, when the flow is then elevated to a high flow condition, that high flow effectively scours out the previously settled material and then is carried downstream, thereby reducing or eliminating the effectiveness of the stormwater treatment device.
As a further problem in dealing with the differing flows, the high flow streams of water carry additional trash and larger solids that are only picked up and carried along by the higher flows and therefore there is a need to be able to capture that trash and larger solids with the stormwater treatment device.
Accordingly, there have been various stormwater treatment devices that provide for the separate treatment of the high flows and the low flows, and one typical manner of such treatment is to separate the high flow streams of water from the low flow streams in the water treatment device such that the high flows can be dealt with in a separate area that can effectively deal with those additional larger solids and trash while also preventing those high flow streams of water from scouring out the material that has been removed and therefore settled in the low flow treatment areas of the stormwater treatment device.
One of such stormwater treatment devices is shown and described in my co-pending U.S. patent application Ser. No. 10/247,875, filed Sep. 20, 2002, and entitled APPARATUS FOR TRAPPING FLOATING AND NON-FLOATING PARTICULATE MATTER and the disclosure of that patent application is hereby incorporated herein in its entirety by reference. In the stormwater treatment device of that patent application, however, the incoming stream of water to be treated enters an inner chamber in a direction that is perpendicular to the wall of the inner chamber and the water thereby directly hits the wall of the inner chamber where turbulence is created during both high and low flow conditions.
Additionally, the high and low flows are split in two directions but converge at the outlet where, again, turbulence occurs. Certainly, it would be preferable for the water treatment device to have the various streams of water pass smoothly through the treatment device and not be subjected to turbulence.
As a further difficulty with the stormwater treatment device of the aforesaid patent application, the device requires the installation of two sets of weirs, that is, two high and two low weirs in carrying out the treatment of the water flowing therethrough and those weirs must be installed in the field during the installation of the treatment device at the intended site. That use of two sets of weirs, however, along with the centralized location of the inner chamber, offers limited space within the overall water separation device by the use of the multiple weirs and is insufficient to allow a worker to enter the device to carry out that installation.
Thus, there is a desire for an efficient and cost effective means for trapping debris in storm water that overcomes the difficulties of the aforedescribed stormwater treatment devices and yet which is effective at trapping both floating and non-floating particulate matter. Such an apparatus should be simple in its design and be able to be produced at low cost. The device should be flexible in varying field conditions, i.e., able to satisfy varying size and height requirements and be able to connect efficiently to the non-linear junction points that inevitably occur in piping systems. Finally, such a device should be easy to maintain and not be prone to clogging or need the regular changing of filtering materials.